1. Field of the Invention
The present invention relates to a thin-film magnetic head, a magnetic head assembly and a magnetic disk drive apparatus that have a magnetoresistive effect (MR) read head element, and method for manufacturing a thin-film magnetic head.
2. Description of the Related Art
Along with the development of high capacity and small hard disk drives (HDD), thin-film magnetic heads with high sensitivity and output are required. For this requirement, characteristic of a giant magnetoresistive head, which has a giant magnetoresistive effect (GMR) read head element, has been improved. On the other hand, a tunnel magnetoresistive head, which has a tunnel magnetoresistive effect (TMR) read head element, has been actively developed. The ratio of resistance change of TMR heads is expected to be more than double compared to the one of GMR heads.
A lower shield layer located below a MR layer and an upper shield layer located above the MR layer get thinner for a MR read head element of a thin-film magnetic head with high capacity. Thinner the lower and the upper shield layer with respect to widths of them, more magnetic fluxes are concentrated to an edge area of them. It shows the same tendency with a lower and an upper shield layers which are formed as a thin-film by plating method. However, this tendency is more apparent with a lower and an upper shield layers which are formed by ion milling after sputtering to thin the thickness, i.e. a film is formed by sputtering, and then patterning is performed by ion milling. This is because a cross-section of an edge area of a shield layer has a sharply peaked shape regardless a width and a thickness of it, if the shield layer is formed by ion milling.
FIG. 1 is a cross-section view of an edge area of a lower shield layer, which is formed as thin-film, viewed from air bearing surface (ABS) of a thin-film magnetic head.
As shown in FIG. 1, the edge area 10a of the lower shield layer 10 is skew, not perpendicular, with respect to a lamination plane, in case a film thickness of the lower shied layer 10 is thin, and the edge area 10a has a sharply peaked shape. For this reason, magnetic fields, which are applied for example from outside or a magnetic write head element, are concentrated to the edge area 10a. Unnecessary writing to a magnetic disk, which faces the thin-film magnetic head, occurs by the concentrated magnetic fields. Problem caused by the shape of the edge area of the lower and the upper shield layers to the magnetic disk is more apparent with perpendicular magnetic recording heads compared to longitudinal magnetic recoding heads.
To solve the problem caused by leaked magnetic fluxes from a thin-film magnetic head, JP patent publication 2001-6121A discloses a thin-film magnetic head, which has shunt parts at leading end area close to a magnetic disk. According to JP patent publication 2001-6121A, recoding fringe caused by leaked magnetic fluxes from a recording gap is reduced by leading leaked magnetic fluxes to the shunt parts.
However, JP patent publication 2001-6121A discloses the configuration for leading leaked magnetic fluxes from the recording gap of a magnetic write head element to shunt parts, which are provided both sides of the recording gap, but it does not disclose how to reduce the leakage of magnetic fluxes. Therefore technique disclosed in JP patent publication 2001-6121A cannot be applied to prevent the leakage of magnetic fluxes from an edge area of a lower or an upper shield layer. More specifically it is very difficult to form shunt parts near a lower and an upper shield layers of a MR read head element in terms of space. Event though shunt parts are formed, they do not reduce the leakage of magnetic fluxes from the edge areas of the lower and the upper shield layers.